Speciation is the process by which a single species diverges into two or more descendent species. Although potential mechanisms of speciation are well known, the relative importance of different mechanisms remains poorly understood, due to the long timescales involved and the possible confounding effects of subsequent evolutionary changes and of extinction. We use analyses of evolutionary relationships and diversity patterns among present-day species to test general theories about the importance of geographical isolation and divergent selection in speciation.

The probability of speciation on oceanic islands depends on the size of the island but also on the levels of gene flow (measured by Fst) of the organisms concerned – taxa that disperse further speciate less. Figure 4 from Kisel and Barraclough (2010).